With the continuous development of integrated circuit (IC) manufacturing technologies, the copper (Cu) interconnect has been widely used in the back-end-of-line (BEOL) process. Comparing with the aluminum (Al) interconnect, the resistivity of Cu in the Cu interconnect structure is relatively low; and the anti-electromigration ability is higher.
With the continuous shrinking of the critical dimension (CD) of devices, to reduce the resistance-capacitance (RC) delay, it requires to increase the conductivity of the interconnect structure. Thus, the seed-free Cu interconnect technique has attracted more and more attentions. The conventional adhesion barrier layer has a relatively high resistivity; and it cannot be used as the seed layer for directly electroplating Cu. However, ruthenium (Ru) has a lower resistivity than Cu; a better adhesion with Cu; and is able to achieve a direct electroplating of Cu. Thus, Ruthenium (Ru)-containing layer has been gradually introduced in the Cu interconnect technique; and the Ruthenium (Ru)-containing layer can be used as the wetting layer of the Copper (Cu)-containing layer.
However, introducing the Ruthenium (Ru)-containing layer is easy to deteriorate the quality and the performance of the Cu interconnect structure. The disclosed methods and semiconductor structures are directed to solve one or more problems set forth above and other problems in the art.